Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;

import java.io.IOException;
import java.io.InputStream;

public class Main {
    /**
     * Read a text file into a String, optionally limiting the length.
     * 
     * @param file
     *            to read (will not seek, so things like /proc files are OK)
     * @param max
     *            length (positive for head, negative of tail, 0 for no limit)
     * @param ellipsis
     *            to add of the file was truncated (can be null)
     * @return the contents of the file, possibly truncated
     * @throws IOException
     *             if something goes wrong reading the file
     */
    public static String readTextFile(File file, int max, String ellipsis) throws IOException {
        InputStream input = new FileInputStream(file);
        try {
            long size = file.length();
            if (max > 0 || (size > 0 && max == 0)) { // "head" mode: read the
                                                     // first N bytes
                if (size > 0 && (max == 0 || size < max))
                    max = (int) size;
                byte[] data = new byte[max + 1];
                int length = input.read(data);
                if (length <= 0)
                    return "";
                if (length <= max)
                    return new String(data, 0, length);
                if (ellipsis == null)
                    return new String(data, 0, max);
                return new String(data, 0, max) + ellipsis;
            } else if (max < 0) { // "tail" mode: keep the last N
                int len;
                boolean rolled = false;
                byte[] last = null, data = null;
                do {
                    if (last != null)
                        rolled = true;
                    byte[] tmp = last;
                    last = data;
                    data = tmp;
                    if (data == null)
                        data = new byte[-max];
                    len = input.read(data);
                } while (len == data.length);

                if (last == null && len <= 0)
                    return "";
                if (last == null)
                    return new String(data, 0, len);
                if (len > 0) {
                    rolled = true;
                    System.arraycopy(last, len, last, 0, last.length - len);
                    System.arraycopy(data, 0, last, last.length - len, len);
                }
                if (ellipsis == null || !rolled)
                    return new String(last);
                return ellipsis + new String(last);
            } else { // "cat" mode: size unknown, read it all in streaming
                     // fashion
                ByteArrayOutputStream contents = new ByteArrayOutputStream();
                int len;
                byte[] data = new byte[1024];
                do {
                    len = input.read(data);
                    if (len > 0)
                        contents.write(data, 0, len);
                } while (len == data.length);
                return contents.toString();
            }
        } finally {
            input.close();
        }
    }
}